The response of an individual to a spontaneous or intentionally generated event involves a number of complex neurological and physiological steps including detection, conductive neural pathways, synaptic connections, perception, cognition, and neuro-muscular control. Normal activities or disorders in any of the anatomical structures or chemistries involved in these steps, as well as physiological awareness and training, can affect an individual's response magnitudes and reaction times. An unobtrusive device that measures reaction times and/or other responses of an individual over brief (i.e., seconds to minutes) or prolonged (i.e., days or even years) time periods has a number of medical, sports training, human factors, safety, diagnostic, military, law enforcement, gaming, and other applications.
Applications that involve sensing and machine vision are becoming increasingly common-place. In part, this has arisen as a result of technological advances in the electronics and software development industries, and decreases in the cost of sensors, cameras, and information processing units. For example, recent advances in accelerometers based on microelectromechanical systems (MEMS) techniques have made them inexpensive, miniature, sensitive, robust, low-power, multi-axial (within a single package), and easy to use. Accelerometers can be used to sense gravitational orientation as well as multi-dimensional movements.
Similarly, cameras that employ complementary metal-oxide semiconductor (CMOS) or charge-coupled device (CCD) approaches, can be inexpensive, miniature, optically sensitive, low-power, robust, and high resolution. Using such cameras and image processing units, automated object identification and tracking are increasingly being used in a number of diagnostic, human performance, commercial, and control applications.
With the exception of events that cause head trauma, most movements of the head are relatively slow (e.g., less than about ten Hertz (10 Hz)). Thus, sample rates to accurately monitor head movement may be in the range of tens of samples/second. Similarly, most measurements of eye, eyelid, and pupillary responses and reaction times, which may have reaction times in the range of tenths of a second to seconds, require the frame rates commonly available in modern, household cameras and video displays (i.e., 30-120 frames per second). Research laboratories and some other applications may demand measurements from accelerometers and cameras that are capable of higher sample rates but at an increased cost; however, eyewear and headwear devices can take advantage of commonly-available miniature, low-power cameras and sensing components.
Many head- and eye-tracking systems use cameras and illuminators that are located at a considerable distance (e.g., greater than about ten centimeters (10 cm)) from the wearer's head. As the distance away from the wearer's head is increased, a head/eye tracking apparatus generally becomes less obtrusive; however, it becomes increasingly difficult to accurately measure the location of a wearer's head and/or eyes because of the need for higher spatial resolution by cameras. Also, wide-ranging head movement may cause complete loss of the ability to track the location of a wearer's eye and its components.
With the advent of modern-day microelectronics and micro-optics, it is possible to unobtrusively mount the components for measuring reaction times or other responses on eyewear (e.g., eyeglasses frames) or headwear (e.g., helmet, mask, goggles, virtual reality display) including those devices disclosed in U.S. Pat. Nos. 6,163,281, 6,542,081, 7,488,294, or 7,515,054, the entire disclosures of which are expressly incorporated by reference herein. The use of low-power and miniature cameras, sensors, and electronics permits a head-mounted system to be non-tethered through the use (optionally) of a battery power source. Furthermore, recent advances in wireless telecommunications allow reaction time results to be transmitted in real-time to other computing, data storage, or control devices. As a result of these technological advances in a number of fields, an eyewear- or headwear-based response and reaction time monitoring system may be unobtrusive, light-weight, low-power, portable, and convenient to use.
Non-invasive tools for physiological monitoring and medical diagnostics are increasingly commonplace in clinics, hospitals, research laboratories, and even homes and public areas, such as grocery stores and pharmacies. If such tools are constructed to be unobtrusive, simple to use, and portable; they gain even further potential in their acceptance by the general public and subsequent applications to monitor longer-term response trends (versus one-time or “snap-shot” measurements). This is in addition to their capability to react in real-time if certain conditions are encountered; for example, if a state of drowsiness is determined while driving a vehicle.
Monitoring responses of the head and eyes is particularly useful in assessing both central and peripheral nervous system physiological function and disorders. For example, reaction times and/or other responses of the pupil are influenced by a chain of anatomical structures including photosensitive ganglion cells and the retinohypothalamic tract within the optic nerve, the pretectal nucleus within the upper midbrain, and the Edinger-Westphal nucleus with axons running along left and right oculomotor nerves that synaptically connect to ciliary ganglion nerves that, in turn, innervate constrictor muscles of the iris. Disorders or conditions (e.g., the presence of barbiturates) that affect any of the structures within this chain may produce consequential changes in reaction times and/or other responses that may be monitored non-invasively and unobtrusively. Initial constriction of the pupils by alcohol or opioids; or dilation by a wide range of drugs including lysergic acid diethylamide (LSD), cocaine, amphetamines, 3,4-methylenedioxymethamphetamine (MDMA, also known as ecstasy), mescaline, and so on; may also affect measured responses and reaction times.
Reaction times and/or other responses may be used to probe even deeper into cognitive functions of the brain. An unobtrusive tool for substantially continuously monitoring reaction times and/or other responses of the head and eyes may lend valuable quantitative measurements to perceptions that we are all familiar with, including sensing fear, alarm, or whether someone is telling the truth. This may result in a number of applications including substantially continuous monitoring of the elderly for diagnostic purposes as well as an input in determining emergency situations. An example of an application where a clinician may take advantage of the quantitative nature of such measurements is in the assessment of many anxiety disorders such as post-traumatic stress disorder (PTSD). Measuring avoidance behaviors and difficulty concentrating along with exaggerated responses to events that startle may be monitored and used for assessment and tracking of such disorders.
Measurements of evoked pupillary responses have been used in a wide range of assessments of “cogitative load” or “mental effort” and associated disorders. Under normal physiological conditions, the presentation of multiple stimuli in timed sequences can increase pupillary dilation responses. An increase in this effect may be indicative of various forms of dementia.
Conversely, a goal of sports training is to improve performance by decreasing reaction times. Anticipation and experience may each reduce reaction times by (as generally believed) reducing any decision times and strengthening synaptic connections. An unobtrusive device that may measure reaction times and/or other responses over prolonged periods may be valuable in monitoring, for example, the effectiveness of training regimes.